If they plan to use MARCS for regular, daily operations, they're pretty much stuck with the user fees. Unless the radios are LEUO (Local Emergency Use Only) radios, everybody pays them.
That being said, however, $20/month per radio is a lot cheaper for each of them than spending the considerable sums it would take to either buy all new equipment to improve and upgrade conventional radio systems on their existing frequencies, or even more money for trunked radio systems of their own. Add to that the long-term costs of system maintenance and repair (which they won't have to worry about anymore), and MARCS becomes a pretty good deal for them.
This doesn't even take into consideration the hidden costs of interoperability; operating on MARCS can reduce or even eliminate these.
BTW, this grant was awarded a few months ago....
http://www.radioreference.com/forums/showthread.php?t=93806